Structure and Performance of High Mobility Amorphous Indium-Oxide-Based Materials for Transparent Thin Film Transistors

Brown University, Providence RI

Investigators

Abstract

Technical: This project seeks to advance fundamental understanding of defect doping and interface structure of an emerging class of high-mobility semiconducting metal oxide materials, such as indium zinc oxide. Thin film transistors (TFTs) based on amorphous metal oxides offer the promise of transparent electronics along with significant performance and processing advantages over the amorphous Si and organic alternatives. The rate of development of oxide-based transparent TFT device technology has accelerated while critical/limiting underlying fundamental materials issues concerning native defect doping and the nano-scale structure of amorphous metal oxide semiconductors and their oxide/dielectric interfaces remain poorly understood. At present, the oxide-electronics literature is silent on critically important questions concerning carrier mobility and generation in the low carrier concentration regime and little is reported on the stability of oxide-channel TFT devices with respect to, for example, threshold voltage shift and channel conductivity. In this project, a gate-down test-TFT device will be used to analyze field effect transport behavior as a function of the processing and chemistry of channel and gate materials. Microstructural characterization tools such high resolution transmission electron microscopy will be used for interface morphology evaluation, while electron scattering and radial distribution function analysis along with fluctuation microscopy will provide insight into the near- and medium-range structure of the amorphous phase. Electronic characterization such as field effect transport and Hall measurements will be used to provide insight into the effect of processing on point-defect-scale features. Insights into the structure and formation of native donor defects will be examined using a novel defect volume measurement approach that relates film stress to measurable carrier density changes. Non-technical: The project addresses basic research issues in a topical area of materials science with high technological relevance, and is expected to provide scientific understanding of a class of semiconducting oxide materials, which could find applications for low cost, large-area electronics for displays, sensors, smart windows, and photovoltaics. The project provides training of both graduate and undergraduate students in research in an interdisciplinary. Strong connections between the PI and local industry will further enhance the value of the professional training experience for the students. The project also includes educational outreach activities to local schools, such as Science Day for middle school students and hands-on grade-appropriate demonstration of transparent thin film transistors.